Service for quick and easy cluster-aware logging into date-bound files.

Use LogfileService to log events, data and/or errors into locally generated logfiles. Each logfile is date stamped and only contains logs for that date. Log entries are time stamped to milliseconds.

By default, if application runs on cluster, each cluster node logs into separate file. If cluster identifier is set, then logs are written into single file for all cluster nodes, and log entries are stamped with worker id and process id.

Target: ES2022 [NodeJS][ESM+CJS].

Use functions trace, debug, info, warn, and error to write logs conditionally, depending on specified minimum log level. For example, if minimum log level is INFORMATION then trace and debug will not write into a logfile. Use functions fail and log to write logs unconditionally.

LogfileService allows logging with the following levels:

• TRACE
• DEBUG
• INFORMATION
• WARNING
• ERROR
• FAILURE

• dir: Logfile directory, defaults to current working directory.
• tag: Logfile tag to identify logging application, defaults to empty string.
• ext: Logfile extension, defaults to 'log'.
• utc: If true date-time values are in UTC, defaults to false.
• stack: If true writes error stack trace if available, defaults to false.
• stdout: If true additionally writes logs to stdout, defaults to false.
• level: Minimum log level, errors and failures are always logged, defaults to INFORMATION.
• cluster: Logfile cluster identifier if logs to be written into a single file for all cluster nodes. By default, each cluster node logs into separate logfile [dir|CWD]/YYYY-MM-DD[.tag].[worker-id].[ext|log], where CWD is current working directory.

If multiple instances of LogfileService are used, make sure that each instance has different dir/tag/ext combination, and cluster identifier.

Sample code to log events and errors:

...
const logf = new LogfileService( { tag: 'test', utc: true } );
...
logf.info( 'log some info' );
logf.log( 'logging some data', { val: 'abc', anotherValue: 'def' }, [ 1, 2 ] );
...
logf.error( 'something went wrong', new Error( 'Test Error' ), obj );
...

Sample log file 2023-07-12.test.log:

|14:18:57|
|349| log some info
|411| logging some data
{"val":"abc","anotherValue":"def"}
[1,2]
|14:18:58|
|010| something went wrong
Test Error
{"objProp1":"a"}